VIRTUAL VIBRATION TESTING SIMULATION OF VARIABLE MASS SYSTEM

For the structures worked in the aerospace field, the dynamic characteristics and safety are significantly influenced by variations of system mass due to fuel consumption or component detachment during the operation of aerocraft. Virtual vibration testing is valuable to predict the vibration responses of the variable mass system. The finite element equations for a cylindrical shell system with variable-mass internal filler were derived based on the element birth and death method. A finite element model of the cylindrical shell and variable-mass internal filler was established using Ansys, focusing on the impact of internal filler reduction on the dynamic characteristics of the cylindrical shell system. The relationship between the first-order bending natural frequency of the cylindrical shell and the internal filling ratio was obtained through modal analysis. Virtual vibration simulations of the variable-mass system were performed using the element birth and death method to calculate the vibration response of the variable-mass system, analyse the influence of mass variation on the vibration response of the cylindrical shell, and study the effect of element discretization accuracy on the simulation results. The results show that the first-order bending frequency of the cylindrical shell is insensitive to mass variation when the filling ratio is between 0 and 0.2. The smaller the ratio of the mass of the discretized element to the total mass, the more reliable the simulation result. The variable-mass system has a fixed range of resonant bandwidth, with larger resonant peaks appearing at both ends of the bandwidth.